Electrodynamics in an LTB scenario

In this article we analyze the electrodynamics in curved space-time in LTB metric. We calculate the most general scale factor in this inhomogeneous Universe. We also study the presence of electromagnetic field bubbles in the Universe.Comment: 9 pages, Accepted for publication in the EPJ

A new approach to the propagation of light-like signals in perturbed cosmological backgrounds

We present a new method to compute the deflection of light rays in a perturbed FLRW geometry. We exploit the properties of the Geodesic Light Cone (GLC) gauge where null rays propagate at constant angular coordinates irrespectively of the given (inhomogeneous and/or anisotropic) geometry. The gravitational deflection of null geodesics can then be obtained, in any other gauge, simply by expressing the angular coordinates of the given gauge in terms of the GLC angular coordinates. We apply this method to the standard Poisson gauge, including scalar perturbations, and give the full result for the deflection effect in terms of the direction of observation and observed redshift up to second order, and up to third order for the leading lensing terms. We also compare our results with those presently available in the literature and, in particular, we provide a new non trivial check of a previous result on the luminosity-redshft relation up to second order in cosmological perturbation theory.Comment: 37 pages, no figures. Typos corrected, comments and references added. Version accepted for publication in JCA

An exact Jacobi map in the geodesic light-cone gauge

The remarkable properties of the recently proposed geodesic light-cone (GLC) gauge allow to explicitly solve the geodetic-deviation equation, and thus to derive an exact expression for the Jacobi map J^A_B(s,o) connecting a generic source s to a geodesic observer o in a generic space time. In this gauge J^A_B factorizes into the product of a local quantity at s times one at o, implying similarly factorized expressions for the area and luminosity distance. In any other coordinate system J^A_B is simply given by expressing the GLC quantities in terms of the corresponding ones in the new coordinates. This is explicitly done, at first and second order, respectively, for the synchronous and Poisson gauge-fixing of a perturbed, spatially-flat cosmological background, and the consistency of the two outcomes is checked. Our results slightly amend previous calculations of the luminosity-redshift relation and suggest a possible non-perturbative way for computing the effects of inhomogeneities on observations based on light-like signals.Comment: 26 pages, no figures. Inconsequential modification of an equation, comments and references added. Version accepted for publication in JCA

Cosmic acceleration and f(R)f(R) theory: perturbed solution in a matter FLRW model

In the present paper we consider $f(R)$ gravity theories in the metric approach and we derive the equations of motion, focusing also on the boundary conditions. In such a way we apply the general equations to a first order perturbation expansion of the Lagrangian. We present a model able to fit supernovae data without introducing dark energy.Comment: 10 pages, 1 figur

Factor analysis for the choice of a criterion of wine grape (Vitis vinifera) maturity in warm regions

Factor analysis has been applied to choose a criterion of wine grape (Vitis vinifera) maturity. Thus, six variables could be reduced to two factors. The first factor includes pH, total acidity, °B x pH, °B/acidity, but pH has the highest loading. The second factor has the highest loading for °Balling. pH and °Balling are suggested to be important variables for determining the maturity of wine grapes in warm regions.Analyse de facteurs pour le choix d'un critère de maturité des raisins de cuve dans les régions chaudesNous avons appliqué l'analyse de facteurs en vue de choisir un critère pour la maturité du raisin. Cette analyse a permis de réduire six variables à deux facteurs. Le premier facteur comprend le pH, l'acidité totale, °B/acidité, dont le pH a le plus haut «loading». Le second facteur a le plus haut «loading» pour le °Balling. Nous suggérons d'attacher de l'importance au pH et au °B quant à la détermination du degré de maturité des variétés de raisins de cuve dans le commerce provenant de plantes obtenues par croisements dans les régions chaudes

The heritability of fruit ripening date in Vitis vinifera L.

An analysis of the inheritance of fruit ripening date in V. vinifera grapes, based on data collected on 2200 genotypes from 55 families generated by crosses among 35 parents, reveals that this trait is controlled by genes highly additive in their effects. The heritability of this trait was estimated to be 0.50 ± 0.04. The expected average gain of the progeny of randomly mated parents ranked in the upper 10 percent of the parental generation was calculated. The results indicate that relatively rapid genetic gain can be expected in this population by selecting parents on the basis of their own performance and subsequent mating inter se.Die Erblichkeit des Reifungszeitpunktes der Trauben von Vitis vinifera L.An 2200 Genotypen von Vitis vinifera aus 55 Familien, die aus der Kreuzung von 35 Elternpflanzen hervorgegangen waren, wurde die Vererbung des Reifungstermins der Trauben analysiert. Es zeigte sich, daß dieses Merkmal durch Gene bestimmt wird, die in hohem Maße additiv wirken. Der Heritabilitätskoeffizient des Merkmals wurde auf 0,50 ± 0,04 geschätzt. Der durchschnittlich zu erwartende Leistungszuwachs bei der Nachkommenschaft zufällig gepaarter Eltern, die zu den oberen 10 Prozent ihrer Generation zählten, wurde errechnet. Die Befunde weisen darauf hin, daß bei einer solchen Population ein relativ rascher Kreuzungserfolg erwartet werden kann, wenn man die Eltern aufgrund ihrer Leistungseigenschaften auswählt und sie anschließend untereinander kreuzt

Influence of drought stress on shoot, leaf growth, leaf water potential, stomatal resistance in wine grape genotypes (Vitis vinifera L.)

Most physiological and morphological tests suggested in the literature for drought resistance are too sophisticated, time-consuming and sometimes unreliable. Quantitative data have indicated that plant growth is very sensitive to water stress. Therefore the elongation rate of shoot and leaf characters (petiole, lamina), which are simple parameters to measure, and leaf water potential and stomatal resistance were determined on 5 sampling dates under water stress and non-stress conditions in different wine grape varieties (Vitis vinifera). The leaf water potential and stomatal resistance show very little variability as well as low correlation in the wine grape varieties considered. On the contrary, the weekly elongation rate of shoot and leaf characters (petiole, lamina) shows high variability and highly significant correlations. Thus some of these morphological characters (lamina and shoot elongation) might be used as test in the early phase (at seedling stage) of a breeding selection program for drought resistance in Vitis

Analysis of genetic relationships among Muscat grapevines in Apulia (South Italy) by RAPD markers

Two hundred 10-mer primers of arbitrary nucleotide sequence were used to study the genetic relationships among Muscat grapevines in Apulia. The coefficients of similarity of these genotypes were determined with 484 polymorphic RAPD bands (profiles). The bootstrap sampling analysis revealed that the number of RAPD bands was suitable to estimate the coefficients of similarity. The pattern of aggregation among genotypes (cluster analysis, principal coordinate analysis) indicates a diversity among the Muscats in Apulia except for Moscato Reale and Moscato Canelli, which were closely related

Comparing the luminosity distance for gravitational waves and electromagnetic signals in a simple model of quadratic gravity

We compute the modified friction coefficient controlling the propagation of tensor metric perturbations in the context of a generalized cosmological scenario based on a theory of gravity with quadratic curvature corrections. In such a context we discuss the differences between gravitational and electromagnetic luminosity distance, as well as the differences with the standard results based on the Einstein equations. We present numerical estimates of the modified luminosity distance on the cosmic redshift scale typical of Supernovae and standard sirens.Comment: 21 pages, 4 figures, published in General Relativity and Gravitatio